package prolog3d;

import javax.media.j3d.*;
import javax.vecmath.*;

// vertices could be at (0, 0, 0), (0, 1, 1), (1, 0, 1), (1, 1, 0)
public class Tetra extends Simple {
  Tetra() {
    super(new TetraShape());
    transformScale(defScale);
  }
  
  public Tetra(Color3f c,float t) {
    super(new TetraShape(),makeApp(c,t));
    transformScale(defScale);
  }
}

class TetraShape extends Shape3D {
  private static final float sqrt3 = (float) Math.sqrt(3.0);
  private static final float sqrt3_3 = sqrt3 / 3.0f;
  private static final float sqrt24_3 = (float) Math.sqrt(24.0) / 3.0f;

  private static final float ycenter = 0.5f * sqrt24_3;
  private static final float zcenter = -sqrt3_3;
 
 
  private static final Point3f p1 = new Point3f(-1.0f, -ycenter, -zcenter);
  private static final Point3f p2 = new Point3f(1.0f, -ycenter, -zcenter);
  private static final Point3f p3 = new Point3f(0.0f, -ycenter, -sqrt3 - zcenter);
  private static final Point3f p4 = new Point3f(0.0f, sqrt24_3 - ycenter, 0.0f);
  
  private static final Point3f[] verts = {
                                           p1, p2, p4,	// front face
                                           p1, p4, p3,	// left, back face
                                           p2, p3, p4,	// right, back face
                                           p1, p3, p2,	// bottom face
                                         };

  private TexCoord2f texCoord[] = {
                                    new TexCoord2f(0.0f, 0.0f),
                                    new TexCoord2f(1.0f, 0.0f),
                                    new TexCoord2f(0.5f, sqrt3 / 2.0f),
                                  };

  public TetraShape() {
    int i;

    TriangleArray tetra = new TriangleArray(12, TriangleArray.COORDINATES |
      TriangleArray.NORMALS | TriangleArray.TEXTURE_COORDINATE_2);

    tetra.setCoordinates(0, verts);
    for (i = 0; i < 12; i++) {
      tetra.setTextureCoordinate(0, i, texCoord[i%3]);
    }

    int face;
    Vector3f normal = new Vector3f();
    Vector3f v1 = new Vector3f();
    Vector3f v2 = new Vector3f();
    Point3f [] pts = new Point3f[3];
    for (i = 0; i < 3; i++) pts[i] = new Point3f();

    for (face = 0; face < 4; face++) {
      tetra.getCoordinates(face*3, pts);
      v1.sub(pts[1], pts[0]);
      v2.sub(pts[2], pts[0]);
      normal.cross(v1, v2);
      normal.normalize();
      for (i = 0; i < 3; i++) {
        tetra.setNormal((face * 3 + i), normal);
      }
    }
    this.setGeometry(tetra);
    this.setAppearance(new Appearance());
  }
}
